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16th January 2024
Diagnosis
The American College of Rheumatology (ACR) have proposed an updated 2022 classification criteria for EGPA; however, this was only intended to distinguish between vasculitides rather than for diagnostic use.
The table below summarises some investigations used to diagnose EGPA, with the expected associated findings.
| Investigation | Results/findings |
|---|---|
| Urinalysis | Microscopic haematuria or proteinuria may be present, indicative of glomerulonephritis. |
| Lung function | Demonstrates reversible airway obstruction, in line with an asthma presentation. |
| Blood tests | Eosinophil count is usually more than 10% of the total white cell count (WCC), ESR and CRP can help evaluate inflammation levels but are non-specific for EGPA, deranged U&Es may indicate glomerulonephritis, proBNP will be raised if concurrent heart failure is present, serum IgE is usually raised. p-ANCA/MPO-ANCA is positive in at least one-third of patients with EGPA on immunoassay. |
| Imaging | Chest X-ray may show consolidation and nodules (consistent with granulomas) – these findings can be transient and migratory. Any abnormalities should be further evaluated with a dedicated HRCT of the chest, which can show centrilobular nodules, ground glass opacification and bronchial wall thickening. Bronchoscopy is usually performed in those with opacities to rule out alveolar haemorrhage and malignancy. CT pulmonary angiography may be needed if pulmonary embolism is suspected.
Transthoracic echocardiography (TTE) should be performed to evaluate symptoms of heart failure – wall motion abnormalities are common in EGPA. |
| Biopsy | Skin lesions are usually easily sampled, but renal and/or lung biopsies can also be obtained if severe and progressive disease is apparent. Histology typically shows a mixture of granulomas, eosinophilic infiltrates and vasculitis. |
Table 3: Summary of investigations performed to investigate suspected EGPA. Adapted from: Keogh, K. (2022) Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome), Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome) – Symptoms, diagnosis and treatment | BMJ Best Practice. Available at: https://bestpractice.bmj.com/topics/en-gb/942 (Accessed: January 15, 2023) and King Jr, T. (2022) Clinical features and diagnosis of eosinophilic granulomatosis with polyangiitis (Churg-Strauss), UpToDate. Edited by K. Flaherty et al. UpToDate. Available at: https://www.uptodate.com/contents/clinical-features-and-diagnosis-of-eosinophilic-granulomatosis-with-polyangiitis-churg-strauss?search=egpa&source=search_result&selectedTitle=1~143&usage_type=default&display_rank=1#H17 (Accessed: January 15, 2023).
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